System-Level Refrigeration Cycle (2P)

System-level, two-phase refrigeration block in a moist air, thermal liquid, or two-phase fluid network

Since R2023a

• 

Libraries:
Simscape / Fluids / Two-Phase Fluid / Thermodynamic Cycles

Description

The System-Level Refrigeration Cycle (2P) block models a basic refrigeration cycle consisting of a compressor, a condenser, a liquid receiver, a thermostatic expansion valve, and an evaporator. The block models the refrigerant loop within the block in the two-phase fluid domain using the fluid properties specified at port F. The condenser and evaporator external fluids can be part of a moist air, thermal liquid, or two-phase fluid network. The external fluids are the fluids in the condenser and evaporator opposite the refrigerant.

When the compressor is on, the refrigeration cycle consumes power to transfer heat from the evaporator external fluid to the condenser external fluid. The subcomponents provide the specified nominal heat transfer under nominal operating conditions.

Block Structure

This block behaves as a simplified version of this refrigeration cycle made from Simscape™ Fluids™ blocks that model the condenser, compressor, evaporator, expansion device, and liquid receiver:

The refrigerant flows through the loop counterclockwise. The compressor, which is controlled by the signal at port S, sucks in refrigerant vapor and produces a hot, high-pressure vapor, which moves to the condenser. The condenser rejects heat from the refrigerant to the external fluid to condense the refrigerant. The liquid receiver acts as a storage tank for the refrigerant and only allows liquid flow to exit, which helps maintain normal operation even if fluctuating external conditions cause the condenser output to vary. From the tank, the refrigerant flows to the expansion device, which is typically a valve or capillary tube that produces a large pressure loss. The drop in pressure partially vaporizes the refrigerant, which chills it. The refrigerant moves to the evaporator, which absorbs heat from the external fluid to the cold refrigerant to vaporize the refrigerant.

The subcomponents of the System-Level Refrigeration Cycle (2P) block behave the same as these Simscape Fluids blocks in this model, but the equations for the positive displacement compressor, expansion valve, receiver component, and condenser and evaporator subcomponents vary. For more information on the individual components of a refrigeration system, see:

• Compressor (2P)

• Thermostatic Expansion Valve (2P)

• Receiver Accumulator (2P)

The compressor and evaporator components depend on the External fluid for condenser heat transfer and External fluid for evaporator heat transfer parameters. For more information, see:

• System-Level Condenser Evaporator (2P-MA)

• System-Level Condenser Evaporator (2P-TL)

• System-Level Heat Exchanger (2P-2P)

Positive Displacement Compressor Subcomponent

The compressor subcomponent determines the refrigerant mass flow rate for the system. The physical signal input port S controls the compressor operation. When the value at port S is 0, the compressor is off and the mass flow rate is 0. When the value at port S is 1, the compressor runs at the nominal shaft speed, which produces the nominal mass flow rate under nominal operating conditions. To prevent reverse flow, the value of S must be greater than or equal to 0.

The mass flow rate in the compressor is

$$\dot{m}=\frac{{\eta }_v{\dot{V}}_{nominal}S}{v_{in}},$$

where:

• η_v is the volumetric efficiency.

• S is the value of the signal at port S.

• v_in is the inlet specific volume.

• $${\dot{V}}_{nominal}$$ is the nominal volumetric flow rate, which the block determines from the nominal mass flow rate, $${\dot{m}}_{nominal}$$, which depends on the setting of the Capacity specification parameter:

  • When the Capacity specification parameter is Cooling load,

    $${\dot{m}}_{nominal}=\frac{Q_{cooling}}{h_1-h_4},$$

    where Q_cooling is the Nominal evaporator heat transfer parameter, h₁ is the evaporator outlet specific enthalpy, and h₄ is the valve outlet specific enthalpy.

  • When the Capacity specification parameter is Heating load,

    $${\dot{m}}_{nominal}=\frac{Q_{heating}}{h_2-h_3},$$

    where Q_cooling is the Nominal condenser heat transfer parameter, h₂ is the compressor outlet specific enthalpy, and h₃ is the condenser outlet specific enthalpy.

  • When the Capacity specification parameter is Refrigerant mass flow rate, $${\dot{m}}_{nominal}$$ is the value of the Nominal mass flow rate parameter.

The fluid power that the compressor adds to the flow is

$${\Phi }_{fluid}=\dot{m}\frac{h_{out,isen}-h_{in}}{{\eta }_s},$$

where:

• h_out,isem is the specific enthalpy evaluated at the output pressure for an isentropic process.

• h_in is the inlet specific enthalpy.

• η_s is the isentropic efficiency.

  • When Performance specification is Coefficient of performance for cooling or Coefficient of performance for heating, the block solves for η_s by calculating h₂ and using the relation

    $${\text{h}}_2=\frac{h_2^{isen}-h_1}{{\eta }_s}+h_1,$$

    where h₂^isen is the compressor outlet specific enthalpy assuming an isentropic process.

    • When Performance specification is Coefficient of performance for cooling, the block solves for h₂ with $${\text{CoP}}_{cooling}=\frac{h_1-h_4}{h_2-h_1},$$ where CoP_cooling is the Coefficient of performance at nominal conditions parameter.

    • When Performance specification is Coefficient of performance for heating, the block solves for h₂ with $$Co{P}_{heating}=\frac{h_2-h_3}{h_2-h_1}=\frac{h_2-h_4}{h_2-h_1}=Co{P}_{cooling}+1,$$ where CoP_heating is the Coefficient of performance at nominal conditions parameter.

  • When Performance specification is Compressor isentropic efficiency, η_s is the value of the Compressor isentropic efficiency parameter.

The block calculates the volumetric efficiency directly from the inlet and outlet specific volumes

$${\eta }_v=1+C-C\frac{v_{in}}{v_{out}},$$

where:

• C is the clearance volume fraction that the block determines from the nominal operating conditions.

• v_in and v_out are the inlet and outlet specific volumes evaluated at the inlet and outlet pressures.

The compressor subcomponent does not have mechanical rotational ports and does not need to calculate shaft torque. The mechanical power is

$${\Phi }_{mech}=\frac{{\Phi }_{fluid}}{{\eta }_m},$$

where η_m is the mechanical efficiency.

Expansion Valve Subcomponent

The relationship between mass flow rate, which the compressor determines, and the pressure drop across the thermostatic expansion valve subcomponent is

$$\dot{m}=S_{eff}\sqrt{\frac{2}{v_{in}}}\frac{\Delta p}{{\left(\Delta p^2-\Delta p_{lam}^2\right)}^{0.25}},$$

where:

• v_in is the inlet specific volume.

• Δp is the pressure differential over the valve.

• Δp_lam is the pressure threshold for transitional flow. Below this value, the flow is laminar.

The effective valve area depends on the pressure difference between the measured pressure, p_bulb, and the equalization pressure, p_eq

$$S_{eff}=\beta \left[\left(p_{bulb}-p_{eq}\right)-\left(p_{sat}\left(T_{evap}+\Delta T_{static}\right)-p_{sat}\left(T_{evap}\right)\right)\right],$$

where:

• β is a valve constant the block determines from the nominal operating conditions.

• T_evap is the evaporating temperature, which depends on the Pressure specification setting:

  • When Pressure specification is Pressure at specified saturation temperature, T_evap is the value of the Nominal evaporating (saturation) temperature parameter.

  • When Pressure specification is Specified pressure, T_evap is the saturation temperature that corresponds to the value of the Nominal evaporator pressure parameter.

• ΔT_static is the Static (minimum) evaporator superheat parameter.

• p_sat(T_evap) is the fluid saturation pressure as a function of T_evap.

• p_sat(T_evap+ΔT_static) is the fluid saturation pressure as a function of T_evap+ΔT_static.

• p_bulb is the fluid pressure of the bulb. This pressure is the saturation pressure at the evaporator outlet temperature.

• p_eq is the equalization pressure, which is the evaporator pressure for this block.

The effective valve area has limits. The minimum effective valve area, S_eff,min, is

$$S_{eff,\min }=f_{leak}{S}_{eff,nom},$$

where f_leak is the value of the Ratio of leakage to nominal expansion valve opening parameter. The maximum effective valve area, S_eff,mmax, is

$$S_{eff,max}=f_{max}{S}_{eff,nom},$$

where f_max is the value of the Ratio of maximum to nominal expansion valve opening parameter.

Receiver Subcomponent

Excluding the receiver, the block assumes that the refrigerant mass flow rate is the same value through the loop. In the receiver, the total mass is based on the balance between the mass flow rate produced by the compressor and the mass flow rate metered by the expansion valve. The outflow from the receiver subcomponent is always liquid and perfectly insulated from the environment.

The liquid mass fraction in the receiver subcomponent is

$$\text{M }\frac{d{x}_{liq}}{dt}={\dot{m}}_{liq,in}-{\dot{m}}_{out}-{\dot{m}}_{vaporization}+{\dot{m}}_{condensation},$$

where:

• x_liq is the liquid mass fraction.

• $$\dot{m}$$_liq,in is the portion of the flow in that is liquid.

• $$\dot{m}$$_out is the mass flow rate out of the receiver.

• $$\dot{m}$$_vaporization is the rate of vaporization from the liquid volume to the vapor volume.

• $$\dot{m}$$_condensation is the rate of condensation from the vapor volume to the liquid volume.

The pressure relates to the total mass via the specific volume using the relation

$$\text{M}\left(x_{liq}{v}_{liq}+\left(1-x_{liq}\right)v_{vap}\right)=V,$$

where:

• V is the total receiver volume.

• v_liq is the is the specific volume of the liquid volume.

• v_vap is the is the specific volume of the vapor volume.

Condenser and Evaporator Subcomponents

The condenser and evaporator subcomponents model the refrigerant thermal mass, but do not model fluid volume. For the condenser and evaporator, the energy conservation equation is

$$\text{M }\frac{d{h}_I}{dt}=\dot{m}\left(h_{in}-h_{out}\right)+Q,$$

where:

• M is the constant mass of refrigerant in the component.

• h_I is the refrigerant specific enthalpy at the component internal node.

• $$\dot{m}$$ is the refrigerant mass flow rate.

• Q is the rate of heat transfer from the external fluid to the refrigerant.

• h_in and h_out are the refrigerant specific enthalpy in and out of the component.

Visualize the P-H Diagram

To visualize the refrigeration cycle, use a Probe block from the Simscape > Utilities library to output the variables p_cycle and h_cycle. These variables contain the four pressure and specific enthalpy points of the refrigeration cycle. Connect the variables to the P-H Diagram (2P) block to visualize the refrigeration cycle.

This diagram shows the fluid attributes throughout the system for the refrigerant R-410a. Segment 1 to 2 is the compressor, segment 2 to 3 is the condenser, point 3 is the receiver, segment 3 to 4 is the expansion valve, and segment 4 to 1 is the evaporator.

Assumptions and Limitations

• The block does not model reverse flow and limits the refrigeration cycle to zero and forward flow only. To prevent reverse flow, the block limits the compressor control to zero or forward operation and only models fluid volume in the liquid receiver subcomponent.

• Excluding the liquid receiver, the subcomponents do not model refrigerant fluid volume, which prevents the accumulation of mass in subcomponents. As a result, the refrigerant mass flow rate is the same through the evaporator, compressor, and condenser subcomponents.

• There is no refrigerant pressure loss in the evaporator or condenser.

• The block does not model kinetic energy changes in the refrigerant flow.

• The evaporator subcomponent models approximate pressure dynamics to maintain numerical robustness. However, the condenser subcomponent does not model approximate pressure dynamics, because the condenser pressure is equal to the receiver pressure, which does model pressure dynamics.

• The condenser and evaporator subcomponents only model counter flow because the refrigerant is primarily in the two-phase mixture state within the condenser and evaporator. Consequently, the temperature is uniform across most of the condenser and evaporator, and there is no significant difference between counter flow and cross flow.

• When determining the heat exchanger size, the block ignores the values of the Fraction of condensate entrained as water droplets parameters and assumes that the condensate is not entrained as droplets.

Examples

Model a Refrigeration Cycle

Model considerations for a closed-loop refrigeration cycle.

Data Center Cooling

Models the cooling system of a data center. The system consists of two separate water loops: a chilled water loop and a condenser water loop. The chilled water loop absorbs heat from the server farm and transfers it to the condenser water loop. The condenser water loop rejects this heat to the environment using a cooling tower.

• Open Model

Refrigeration Cycle (System-Level)

Model a refrigeration cycle for a home air conditioning system at an abstract system level using the System-Level Refrigeration Cycle (2P) block. This block simplifies the set up of the refrigeration cycle by encapsulating the entire refrigerant loop in one block.

• Open Model

Refrigeration Cycle (Air Conditioning)

A refrigeration cycle for a home air conditioning system. See Model a Refrigeration Cycle for the recommended steps to build this model in the two-phase fluid domain.

• Open Model

Residential Refrigerator

Models a basic refrigeration system that transfers heat between the refrigerant two-phase fluid and the environment moist air mixture. The compressor drives the R134a refrigerant through a condenser, a capillary tube, and an evaporator. An accumulator ensures that only vapor returns to the compressor.

• Open Model

Ports

Input

S — Signal that operates compressor, unitless

physical signal

Physical signal input that operates the compressor. A value of 0 means the compressor is off. A value of 1 means the compressor is operating at the nominal capacity.

Conserving

F — Refrigerant properties

two-phase fluid

Two-phase fluid conserving port associated with the refrigerant properties. Connect a Two-Phase Fluid Properties (2P) or Two-Phase Fluid Predefined Properties (2P) block to this port. Do not connect any other Two-Phase Fluid blocks to port F because this port acts as an absolute reference.

Ac — Condenser external fluid inlet

moist air | thermal liquid | two-phase fluid

Moist air, thermal liquid, or two-phase fluid conserving port associated with the condenser external fluid inlet. The block assumes that the condenser external fluid flows from port Ac to port Bc. The External fluid for condenser heat transfer parameter controls the port fluid.

Bc — Condenser external fluid outlet

moist air | thermal liquid | two-phase fluid

Moist air, thermal liquid, or two-phase fluid conserving port associated with the condenser external fluid outlet. The block assumes that the condenser external fluid flows from port Ac to port Bc. The External fluid for condenser heat transfer parameter controls the port fluid.

Ae — Evaporator external fluid inlet

moist air | thermal liquid | two-phase fluid

Moist air, thermal liquid, or two-phase fluid conserving port associated with the evaporator external fluid inlet. The block assumes that the evaporator external fluid flows from port Ae to port Be. The External fluid for evaporator heat transfer parameter controls the port fluid.

Be — Evaporator external fluid outlet

moist air | thermal liquid | two-phase fluid

Moist air, thermal liquid, or two-phase fluid conserving port associated with the evaporator external fluid outlet. The block assumes that the evaporator external fluid flows from port Ae to port Be. The External fluid for evaporator heat transfer parameter controls the port fluid.

Output

Qc — Heat rejected in condenser, W

physical signal

Physical signal output port that measures the heat rejected by the refrigerant in the condenser, in W.

Qe — Heat absorbed in evaporator, W

physical signal

Physical signal output port that measures the heat absorbed by the refrigerant in the evaporator, in W.

Pwr — Mechanical power consumed by the compressor, W

physical signal

Physical signal output port that measures the mechanical power consumed by the compressor, in W.

W — Rate of condensation in evaporator, kg/s

physical signal

Physical signal output port that measures rate of condensation in the evaporator external fluid, in kg/s, if the External fluid for evaporator heat transfer parameter is Moist air. If the External fluid for evaporator heat transfer parameter is not moist air, this port outputs 0. The value of this port does not include the portion of condensation that is entrained as water droplets.

Parameters

Refrigeration Cycle

Capacity specification — Method for specifying size of system

Cooling load (default) | Heating load | Refrigerant mass flow rate

Method for specifying the size of the system. You can specify the cooling load, heating load, or the refrigerant mass flow rate.

Nominal condenser heat transfer — Rate of heat transfer in condenser

15 kW (default) | positive scalar

Rate of heat transfer from the refrigerant to the external fluid in the condenser.

Dependencies

To enable this parameter, set Capacity specification to Heating load.

Nominal evaporator heat transfer — Rate of heat transfer in evaporator

15 kW (default) | positive scalar

Rate of heat transfer from the external fluid to the refrigerant in the evaporator.

Dependencies

To enable this parameter, set Capacity specification to Cooling load.

Nominal mass flow rate — Refrigerant mass flow rate

0.005 kg/s (default) | positive scalar

Refrigerant mass flow rate through the cycle.

Dependencies

To enable this parameter, set Capacity specification to Refrigerant mass flow rate.

Pressure specification — Method for specifying condenser and evaporator pressure

Specified pressure (default) | Pressure at specified saturation temperature

Method for providing condenser and evaporator pressures. Select whether to directly provide the pressures or provide the corresponding saturation temperatures.

Nominal condenser pressure — Refrigerant pressure in condenser

1 MPa (default) | positive scalar

Pressure of refrigerant in the condenser.

Dependencies

To enable this parameter, set Pressure specification to Specified pressure.

Nominal evaporator pressure — Refrigerant pressure in evaporator

0.1 MPa (default) | positive scalar

Pressure of refrigerant in the evaporator.

Dependencies

To enable this parameter, set Pressure specification to Specified pressure.

Nominal condensing (saturation) temperature — Condenser refrigerant saturation temperature

333.15 K (default) | positive scalar

Saturation temperature of refrigerant in the condenser.

Dependencies

To enable this parameter, set Pressure specification to Pressure at specified saturation temperature.

Nominal evaporating (saturation) temperature — Evaporator refrigerant saturation temperature

273.15 K (default) | positive scalar

Saturation temperature of refrigerant in the evaporator.

Dependencies

To enable this parameter, set Pressure specification to Pressure at specified saturation temperature.

Nominal condenser subcooling — Operational condenser outlet temperature differential

5 deltaK (default) | positive scalar

Degrees of temperature below saturation temperature at the condenser outlet.

Nominal (static + opening) evaporator superheat — Operational evaporator outlet temperature differential

10 deltaK (default) | positive scalar

Degrees of temperature above saturation temperature at the evaporator outlet. The expansion valve adjusts its valve area to try to maintain this superheat.

Static (minimum) evaporator superheat — Minimum allowable temperature differential at evaporator outlet

5 deltaK (default) | positive scalar

Superheat threshold to close the expansion valve.

Performance specification — Method to specify refrigeration cycle efficiency

Coefficient of performance for cooling (default) | Coefficient of performance for heating | Compressor isentropic efficiency

Method to specify the refrigeration cycle efficiency. Choose based on the coefficient of performance of the cycle for heating, cooling, or the compressor efficiency.

Coefficient of performance at nominal conditions — Ratio of cooling or heating to power consumed for compressor

3 (default) | positive scalar

Ratio of useful cooling or heating by the refrigeration cycle to the power consumed by the compressor.

Dependencies

To enable this parameter, set Performance specification to Coefficient of performance for cooling or Coefficient of performance for heating.

Compressor isentropic efficiency — Ratio of ideal-to-actual change in specific enthalpy across compressor

0.8 (default) | positive scalar

Ratio of ideal, or isentropic, change in specific enthalpy to the actual change in specific enthalpy across the compressor.

Dependencies

To enable this parameter, set Performance specification to Compressor isentropic efficiency.

Compressor volumetric efficiency at nominal conditions — Ratio of volumetric flow rate to displacement rate

0.95 (default) | positive scalar

Ratio of actual volumetric flow rate to the displacement rate of the compressor.

Compressor mechanical efficiency — Efficiency of conversion to torque

0.95 (default) | positive scalar

Ratio of the power delivered to the fluid flow to the power driving the mechanical shaft.

Ratio of maximum to nominal expansion valve opening — Ratio of open valve areas to maintain superheat

1.5 (default) | positive scalar

Ratio of the fully opened valve area to the valve area needed to maintain superheat at nominal conditions.

Ratio of leakage to nominal expansion valve opening — Ratio of closed valve areas to maintain superheat

1e-6 (default) | positive scalar

Ratio of the closed valve area to the valve area needed to maintain superheat at nominal conditions

Expansion valve smoothing factor — Numerical smoothing factor

0.01 (default) | positive scalar

Smoothing factor that introduces a layer of gradual change to the flow response when the valve is in near-open or near-closed positions. Set this value to a nonzero value less than one to increase the stability of your simulation in these regimes.

Condenser refrigerant volume — Volume of condenser refrigerant

0.001 m^3 (default) | positive scalar

Volume of refrigerant in the condenser.

Evaporator refrigerant volume — Volume of evaporator refrigerant

0.001 m^3 (default) | positive scalar

Volume of refrigerant in the evaporator.

Liquid receiver tank volume — Volume of liquid and vapor phases in receiver tank

0.01 m^3 (default) | positive scalar

Total physical volume of liquid receiver tank, including both the volume of liquid and vapor phases.

Initial receiver liquid level — Initial liquid volume fraction in tank

0.5 (default) | positive scalar

Liquid volume fraction in the receiver tank at the start of simulation.

Initialize refrigerant to nominal operating conditions — Whether to specify refrigerant initial conditions

on (default) | off

Whether refrigerant in the cycle starts simulation at the nominal operating conditions based on the nominal operating parameters or specified explicitly with initial condition parameters.

Initial condenser pressure — Initial refrigerant pressure in condenser

1 MPa (default) | positive scalar

Pressure of the refrigerant in the condenser and liquid receiver at the start of simulation.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.

Initial evaporator pressure — Initial refrigerant pressure in evaporator

0.1 MPa (default) | positive scalar

Pressure of the refrigerant in the evaporator at the start of simulation.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.

Initial condenser specific enthalpy [inlet, outlet] — Initial refrigerant specific energy in condenser

[450, 250] kJ/kg (default) | positive scalar | two-element vector

Specific enthalpy of the refrigerant in the condenser at the start of simulation. If you specify this parameter as a vector of two values, the first element is the inlet specific enthalpy value and the second element is the outlet specific enthalpy value. If you enter a scalar, the block assumes that the inlet and outlet specific enthalpy are the same value.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.

Initial evaporator specific enthalpy [inlet, outlet] — Initial refrigerant specific energy in evaporator

[250, 400] kJ/kg (default) | positive scalar | two-element vector

Specific enthalpy of the refrigerant in the evaporator at the start of simulation. If you specify this parameter as a vector of two values, the first element is the inlet specific enthalpy value and the second element is the outlet specific enthalpy value. If you enter a scalar, the block assumes that the inlet and outlet specific enthalpy are the same value.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.

Initial receiver liquid and vapor fully saturated — Whether to specify receiver initial conditions

on (default) | off

Whether the receiver starts the simulation at the saturation equilibrium, meaning the liquid and vapor volumes are both at the saturated state, or uses explicitly specified initial conditions.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions check box.

Initial receiver liquid specific enthalpy — Receiver initial liquid specific enthalpy

500 kJ/kg (default) | positive scalar

Specific enthalpy of the liquid portion of the refrigerant in the receiver at the start of simulation.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions and Initial receiver liquid and vapor fully saturated check boxes.

Initial receiver vapor specific enthalpy — Receiver initial vapor specific enthalpy

3500 kJ/kg (default) | positive scalar

Specific enthalpy of the vapor portion of the refrigerant in the receiver at the start of simulation.

Dependencies

To enable this parameter, clear the Initialize refrigerant to nominal operating conditions and Initial receiver liquid and vapor fully saturated check boxes.

Condenser External Fluid

External fluid for condenser heat transfer — External fluid for heat transfer in condenser

Moist air (default) | Thermal liquid | Two-phase fluid

External fluid for heat transfer in the condenser.

Nominal mass flow rate — Mass flow rate between condenser ports

0.5 kg/s (default) | positive scalar

Mass flow rate from port Ac to port Bc during nominal operating conditions.

Nominal pressure drop — Pressure drop between condenser ports

0.001 MPa (default) | positive scalar

Pressure drop from port Ac to port Bc during nominal operating conditions.

Pressure specification — Method of pressure specification

Specified pressure (default) | Pressure at specified saturation temperature

Method of pressure specification:

• Specified pressure — Specify the nominal inlet pressure.

• Pressure at specified saturation temperature — Specify the nominal saturation temperature that corresponds to the inlet pressure.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid.

Nominal inlet pressure — Pressure at external fluid side inlet of condenser

0.101325 MPa (default) | positive scalar

Pressure at the inlet of the condenser on the external fluid side of the heat exchanger during the nominal operating condition.

Dependencies

To enable this parameter, set either:

• External fluid for condenser heat transfer to Moist air or Thermal liquid.

• External fluid for condenser heat transfer to Two-phase fluid, and set Pressure specification to Specific pressure.

Nominal saturation temperature — Nominal saturation temperature to specify pressure

400 K (default) | positive scalar

Saturation temperature at the outlet of the condenser external fluid side of the heat exchanger during the nominal operating condition. The pressure in the condenser is the corresponding saturation pressure.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid and Pressure specification to Pressure at specified saturation temperature.

Inlet condition specification — Method to describe inlet condition of fluid

Specific enthalpy (default) | Temperature | Vapor quality

Method the block uses to describe the inlet condition of the condenser external fluid at the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid.

Nominal inlet temperature — Temperature at condenser external fluid side inlet

400 K (default) | positive scalar

Temperature at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid and Initial condition specification to Temperature.

Nominal inlet specific enthalpy — Specific enthalpy at condenser external fluid side inlet

500 kJ/kg (default) | positive scalar

Specific enthalpy at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid and Initial condition specification to Specific enthalpy.

Nominal inlet vapor quality — Vapor quality at condenser external fluid side inlet

1 (default) | positive scalar

Vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid and Initial condition specification to Vapor quality.

Inlet humidity specification — Method to describe humidity level at condenser external fluid side inlet

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio | Wet-bulb temperature

Method the block uses to describe the humidity level at the inlet during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air.

Nominal inlet relative humidity — Relative humidity at inlet

0.1 (default) | scalar in the range [0,1]

Relative humidity at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet humidity specification to Relative humidity.

Nominal inlet specific humidity — Specific humidity at inlet

0.01 (default) | scalar in the range [0,1]

Specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet humidity specification to Specific humidity.

Nominal inlet water vapor mole fraction — Mole fraction of water vapor at inlet

0.01 (default) | scalar in the range [0,1]

Mole fraction of the water vapor in a moist air mixture at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet humidity specification to Mole fraction.

Nominal inlet humidity ratio — Humidity ratio at inlet

0.01 (default) | scalar in the range [0,1]

Humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet humidity specification to Humidity ratio.

Nominal inlet wet-bulb temperature — Wet-bulb temperature at the start of simulation

287 K (default) | positive scalar in the range [0,1]

Wet-bulb temperature at the inlet of the external fluid side of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet humidity specification to Wet-bulb temperature.

Inlet trace gas specification — Method to describe trace gas level at inlet

Mass fraction (default) | Mole fraction

Method the block uses to describe the trace gas level at the external fluid side inlet of the condenser during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air.

Nominal inlet trace gas mass fraction — Mass fraction of trace gas at inlet

0.001 (default) | scalar in the range [0,1]

Mass fraction of trace gas in a moist air mixture at the inlet of the external fluid side of the condenser during the nominal operating condition.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet trace gas specification to Mass fraction.

Nominal inlet trace gas mole fraction — Mole fraction of trace gas at inlet

0.001 (default) | scalar in the range [0,1]

Mole fraction of the trace gas in a moist air mixture at the inlet of the external fluid side of the condenser during the nominal operating condition.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and Inlet trace gas specification to Mole fraction.

External fluid volume — Volume of fluid in condenser

0.1 m^3 (default) | positive scalar

Total volume of external fluid in the condenser.

Cross-sectional area at port Ac — Flow area at port Ac

0.01 m^2 (default) | positive scalar

Flow area at the condenser external fluid port Ac.

Cross-sectional area at port Bc — Flow area at port Bc

0.01 m^2 (default) | positive scalar

Flow area at the condenser external fluid port Bc.

Condenser wall thermal mass — Option to model condenser wall heat transfer

Off (default) | On

Whether to include the temperature dynamics of the heat transfer surface.

Condenser wall mass — Condenser heat transfer mass

1 kg (default) | positive scalar

Total mass of the condenser heat transfer surface.

Dependencies

To enable this parameter, select Condenser wall thermal mass.

Condenser wall specific heat — Specific heat of condenser transfer surface

490 J/(K*kg) (default) | positive scalar

Specific heat of the condenser heat transfer surface.

Dependencies

To enable this parameter, select Condenser wall thermal mass.

Initialize to nominal operating conditions — Whether to specify condenser initial conditions

On (default) | Off

Whether to start the simulation at the nominal operating condition or specify a different set of initial conditions using additional parameters.

Initial pressure — Fluid pressure at start of simulation

0.101325 MPa (default) | positive scalar

Condenser external fluid pressure at the start of the simulation.

Dependencies

To enable this parameter, clear the Initialize to nominal operating conditions check box.

Initial fluid energy specification — Initial state of the condenser external fluid

Specific enthalpy (default) | Temperature | Vapor quality | Vapor void fraction | Specific internal energy

Quantity used to describe the initial state of the condenser external fluid.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid and clear the Initialize to nominal operating conditions check box.

Initial temperature — Temperature at start of simulation

293.15 K (default) | positive scalar | two-element vector

Temperature at the start of simulation. If the value is a scalar, then the block assumes that the initial temperature is uniform. If the value is a two-element vector, then the block assumes that the initial temperature varies linearly between the ports condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set either:

• External fluid for condenser heat transfer to Moist air or Thermal liquid and clear the Initialize to nominal operating conditions check box.

• External fluid for condenser heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Temperature.

Initial vapor quality — Vapor mass fraction at start of simulation

0.5 (default) | scalar in the range [0,1] | two-element vector

Condenser external fluid vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor quality is uniform. If the value is a two-element vector, then the block assumes that the initial vapor quality varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Vapor quality.

Initial vapor void fraction — Vapor volume fraction at start of simulation

0.5 (default) | scalar in the range [0,1] | two-element vector

Condenser external fluid vapor void fraction, defined as the volume fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor void fraction is uniform. If the value is a two-element vector, then the block assumes that the initial vapor void quality varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Vapor void fraction.

Initial specific enthalpy — Enthalpy per unit mass at start of simulation

1500 kJ/kg (default) | positive scalar | two-element vector

Condenser external fluid specific enthalpy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific enthalpy is uniform. If the value is a two-element vector, then the block assumes that the initial specific enthalpy varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Specific enthalpy.

Initial specific internal energy — Internal energy per unit mass at start of simulation

1500 kJ/kg (default) | positive scalar | two-element vector

Condenser external fluid specific internal energy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific internal energy is uniform. If the value is a two-element vector, then the block assumes that the initial specific internal energy varies between the condenser ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Specific internal energy.

Initial humidity specification — Method used to describe initial humidity level

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio | Wet-bulb temperature

Method used to describe the initial humidity level in condenser external fluid.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and clear the Initialize to nominal operating conditions check box.

Initial relative humidity — Relative humidity at start of simulation

0.5 (default) | scalar in the range [0,1] | two-element vector

Condenser external fluid relative humidity at the start of simulation. If the value is a scalar, then the block assumes that the initial relative humidity is uniform. If the value is a two-element vector, then the block assumes that the initial relative humidity varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Relative humidity.

Initial specific humidity — Specific humidity at start of simulation

0.01 (default) | scalar in the range [0,1] | two-element vector

Condenser external fluid specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial specific humidity is uniform. If the value is a two-element vector, then the block assumes that the initial specific humidity varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Specific humidity.

Initial water vapor mole fraction — Mole fraction of water vapor at start of simulation

0.01 (default) | scalar in the range [0,1] | two-element vector

Mole fraction of the water vapor in the condenser external fluid at the start of simulation. If the value is a scalar, then the block assumes that the initial water vapor mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial water vapor mole fraction varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Mole fraction.

Initial humidity ratio — Humidity ratio at start of simulation

0.01 (default) | scalar in the range [0,1] | two-element vector

Condenser external fluid humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the start of simulation. If the value is a scalar, then the block assumes that the initial humidity ratio is uniform. If the value is a two-element vector, then the block assumes that the initial humidity ratio varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Humidity ratio.

Initial moist air wet-bulb temperature — Wet-bulb temperature at the start of simulation

287 K (default) | positive scalar in the range [0,1]

Condenser wet-bulb temperature at the start of the simulation.

If the value is a scalar, then the block assumes that the initial wet-bulb temperature is uniform. If the value is a two-element vector, then the block assumes that the initial wet-bulb temperature varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Wet-bulb temperature.

Initial trace gas specification — Method to describe initial trace gas level

Mass fraction (default) | Mole fraction

Method used to describe the trace gas level at the start of simulation.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and clear the Initialize to nominal operating conditions check box.

Initial trace gas mass fraction — Mass fraction of trace gas at start of simulation

0.001 (default) | scalar in the range [0,1] | two-element vector

Mass fraction of trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mass fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mass fraction varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial trace gas specification to Mass fraction.

Initial trace gas mole fraction — Mole fraction of trace gas at start of simulation

0.001 (default) | scalar in the range [0,1] | two-element vector

Mole fraction of the trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mole fraction varies linearly between the ports, with the first element corresponding to port Ac and the second element corresponding to port Bc.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial trace gas specification to Mole fraction.

Initial mass ratio of water droplets to moist air — Ratio of water droplets to moist air

0 (default) | positive scalar

Initial mass ratio of water droplets to moist air.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air and clear the Initialize to nominal operating conditions check box.

Initial condenser wall temperature — Condenser surface temperature at simulation start

293.15 K (default) | positive scalar | two-element vector

Heat transfer surface temperature at the start of simulation. If this value is a scalar, the block assumes that the initial temperature is uniform. If this value is a two-element vector, then the block assumes that the temperature varies linearly between ports Ac and Bc with the first element corresponding to Ac and second element corresponding to Bc.

Dependencies

To enable this parameter, clear the Initialize to nominal operating conditions and Condenser wall thermal mass check boxes.

Relative humidity at saturation — Relative humidity point of condensation

1 (default) | nonnegative scalar

Relative humidity point of condensation. Condensation occurs above this value. In most cases, this value is 1, which is equivalent to 100%. A value greater than 1 indicates a supersaturated vapor.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air.

Water vapor condensation time constant — Time scale for condensation

1e-3 s (default) | positive scalar

Characteristic time scale at which an oversaturated moist air volume returns to saturation by condensing out excess humidity.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air.

Water droplets evaporation time constant — Time scale for evaporation

1e-3 s (default) | positive scalar

Characteristic time scale at which water droplets evaporate to vapor.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air.

Fraction of condensate entrained as water droplets — Fraction of condensate in water droplets

1 (default) | scalar in the range [0,1]

Fraction of the condensate in the moist air that is entrained as water droplets.

Dependencies

To enable this parameter, set External fluid for condenser heat transfer to Moist air.

Evaporator External Fluid

External fluid for evaporator heat transfer — External fluid for heat transfer in evaporator

Moist air (default) | Thermal liquid | Two-phase fluid

External fluid for heat transfer in the evaporator.

Nominal mass flow rate — Mass flow rate between evaporator ports

0.5 kg/s (default) | positive scalar

Mass flow rate from port Ae to port Be during nominal operating conditions.

Nominal pressure drop — Pressure drop between evaporator ports

0.001 MPa (default) | positive scalar

Pressure drop from port Ae to port Be during nominal operating conditions.

Pressure specification — Method of pressure specification

Specified pressure (default) | Pressure at specified saturation temperature

Method of pressure specification:

• Specified pressure — Specify the nominal inlet pressure.

• Pressure at specified saturation temperature — Specify the nominal saturation temperature that corresponds to the inlet pressure.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid.

Nominal inlet pressure — Pressure at external fluid side inlet of evaporator

0.101325 MPa (default) | positive scalar

Pressure at the inlet of the evaporator on the external fluid side of the heat exchanger during the nominal operating condition.

Dependencies

To enable this parameter, set either:

• External fluid for evaporator heat transfer to Moist air or Thermal liquid.

• External fluid for evaporator heat transfer to Two-phase fluid, and set Pressure specification to Specific pressure.

Nominal saturation temperature — Nominal saturation temperature to specify pressure

400 K (default) | positive scalar

Saturation temperature at the outlet of the evaporator external fluid side of the heat exchanger during the nominal operating condition. The pressure in the evaporator is the corresponding saturation pressure.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid and Pressure specification to Pressure at specified saturation temperature.

Inlet condition specification — Method to describe inlet condition of fluid

Specific enthalpy (default) | Temperature | Vapor quality

Method the block uses to describe the inlet condition of the evaporator external fluid at the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid.

Nominal inlet temperature — Temperature at evaporator external fluid side inlet

400 K (default) | positive scalar

Temperature at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid and Initial condition specification to Temperature.

Nominal inlet specific enthalpy — Specific enthalpy at evaporator external fluid side inlet

500 kJ/kg (default) | positive scalar

Specific enthalpy at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid and Initial condition specification to Specific enthalpy.

Nominal inlet vapor quality — Vapor quality at evaporator external fluid side inlet

1 (default) | positive scalar

Vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid and Initial condition specification to Vapor quality.

Inlet humidity specification — Method to describe humidity level at evaporator external fluid side inlet

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio | Wet-bulb temperature

Method the block uses to describe the humidity level at the inlet during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air.

Nominal inlet relative humidity — Relative humidity at inlet

0.1 (default) | scalar in the range [0,1]

Relative humidity at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet humidity specification to Relative humidity.

Nominal inlet specific humidity — Specific humidity at inlet

0.01 (default) | scalar in the range [0,1]

Specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet humidity specification to Specific humidity.

Nominal inlet water vapor mole fraction — Mole fraction of water vapor at the inlet

0.01 (default) | scalar in the range [0,1]

Mole fraction of the water vapor in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet humidity specification to Mole fraction.

Nominal inlet humidity ratio — Humidity ratio at inlet

0.01 (default) | scalar in the range [0,1]

Humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet humidity specification to Humidity ratio.

Nominal inlet wet-bulb temperature — Wet-bulb temperature at the start of simulation

287 K (default) | positive scalar in the range [0,1]

Evaporator wet-bulb temperature in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet humidity specification to Wet-bulb temperature.

Inlet trace gas specification — Method to describe trace gas level at inlet

Mass fraction (default) | Mole fraction

Method the block uses to describe the trace gas level at the external fluid side inlet of the evaporator during the nominal operating condition.

Nominal inlet trace gas mass fraction — Mass fraction of trace gas at inlet

0.001 (default) | scalar in the range [0,1]

Mass fraction of the trace gas in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet trace gas specification to Mass fraction.

Nominal inlet trace gas mole fraction — Mole fraction of trace gas at inlet

0.001 (default) | scalar in the range [0,1]

Mole fraction of the trace gas in a moist air mixture at the inlet of the external fluid side of the evaporator during the nominal operating condition.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and Inlet trace gas specification to Mole fraction.

External fluid volume — Volume of fluid in evaporator

0.1 m^3 (default) | positive scalar

Total volume of external fluid in the evaporator.

Cross-sectional area at port Ae — Flow area at port Ae

0.01 m^2 (default) | positive scalar

Flow area at the evaporator external fluid port Ae.

Cross-sectional area at port Be — Flow area at port Be

0.01 m^2 (default) | positive scalar

Flow area at the evaporator external fluid port Be.

Evaporator wall thermal mass — Option to model evaporator wall heat transfer

Off (default) | On

Whether to include the temperature dynamics of the heat transfer surface.

Evaporator wall mass — Evaporator heat transfer mass

1 kg (default) | positive scalar

Total mass of the evaporator heat transfer surface.

Dependencies

To enable this parameter, select Evaporator wall thermal mass.

Evaporator wall specific heat — Specific heat of evaporator transfer surface

490 J/(K*kg) (default) | positive scalar

Specific heat of the evaporator heat transfer surface.

Dependencies

To enable this parameter, select Evaporator wall thermal mass.

Initialize to nominal operating conditions — Whether to specify evaporator initial conditions

On (default) | Off

Whether to start the simulation at the nominal operating condition or specify a different set of initial conditions using additional parameters.

Initial pressure — Fluid pressure at start of simulation

0.101325 MPa (default) | positive scalar

Evaporator external fluid pressure at the start of the simulation.

Dependencies

To enable this parameter, clear the Initialize to nominal operating conditions check box.

Initial fluid energy specification — Initial state of the evaporator external fluid

Specific enthalpy (default) | Temperature | Vapor quality | Vapor void fraction | Specific internal energy

Quantity used to describe the initial state of the evaporator external fluid.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid and clear the Initialize to nominal operating conditions check box.

Initial temperature — Temperature at start of simulation

293.15 K (default) | positive scalar | two-element vector

Temperature at the start of simulation. If the value is a scalar, then the block assumes that the initial temperature is uniform. If the value is a two-element vector, then the block assumes that the initial temperature varies linearly between the ports evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set either:

• External fluid for evaporator heat transfer to Moist air or Thermal liquid and clear the Initialize to nominal operating conditions check box.

• External fluid for evaporator heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Temperature.

Initial vapor quality — Vapor mass fraction at start of simulation

0.5 (default) | scalar in the range [0,1] | two-element vector

Evaporator external fluid vapor quality, defined as the mass fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor quality is uniform. If the value is a two-element vector, then the block assumes that the initial vapor quality varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Vapor quality.

Initial vapor void fraction — Vapor volume fraction at start of simulation

0.5 (default) | scalar in the range [0,1] | two-element vector

Evaporator external fluid vapor void fraction, defined as the volume fraction of vapor in a liquid-vapor mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial vapor void fraction is uniform. If the value is a two-element vector, then the block assumes that the initial vapor void quality varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Vapor void fraction.

Initial specific enthalpy — Enthalpy per unit mass at start of simulation

1500 kJ/kg (default) | positive scalar | two-element vector

Evaporator external fluid specific enthalpy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific enthalpy is uniform. If the value is a two-element vector, then the block assumes that the initial specific enthalpy varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Specific enthalpy.

Initial specific internal energy — Internal energy per unit mass at start of simulation

1500 kJ/kg (default) | positive scalar | two-element vector

Evaporator external fluid specific internal energy at the start of simulation. If the value is a scalar, then the block assumes that the initial specific internal energy is uniform. If the value is a two-element vector, then the block assumes that the initial specific internal energy varies between the evaporator ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Two-phase fluid, clear the Initialize to nominal operating conditions check box, and set Initial fluid energy specification to Specific internal energy.

Initial humidity specification — Method used to describe initial humidity level

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio | Wet-bulb temperature

Method used to describe the initial humidity level in evaporator external fluid.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and clear the Initialize to nominal operating conditions check box.

Initial relative humidity — Relative humidity at start of simulation

0.5 (default) | scalar in the range [0,1] | two-element vector

Evaporator external fluid relative humidity at the start of simulation. If the value is a scalar, then the block assumes that the initial relative humidity is uniform. If the value is a two-element vector, then the block assumes that the initial relative humidity varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Relative humidity.

Initial specific humidity — Specific humidity at start of simulation

0.01 (default) | scalar in the range [0,1] | two-element vector

Evaporator external fluid specific humidity, defined as the mass fraction of water vapor in a moist air mixture, at the start of simulation. If the value is a scalar, then the block assumes that the initial specific humidity is uniform. If the value is a two-element vector, then the block assumes that the initial specific humidity varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Specific humidity.

Initial water vapor mole fraction — Mole fraction of water vapor at start of simulation

0.01 (default) | scalar in the range [0,1] | two-element vector

Mole fraction of the water vapor in the evaporator external fluid at the start of simulation. If the value is a scalar, then the block assumes that the initial water vapor mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial water vapor mole fraction varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification Mole fraction.

Initial humidity ratio — Humidity ratio at start of simulation

0.01 (default) | scalar in the range [0,1] | two-element vector

Evaporator external fluid humidity ratio, defined as the mass ratio of water vapor to dry air and trace gas, at the start of simulation. If the value is a scalar, then the block assumes that the initial humidity ratio is uniform. If the value is a two-element vector, then the block assumes that the initial humidity ratio varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification Humidity ratio.

Initial moist air wet-bulb temperature — Wet-bulb temperature at the start of simulation

287 K (default) | positive scalar in the range [0,1]

Wet-bulb temperature at the start of the simulation. The block uses this value to calculate humidity.

If the value is a scalar, then the block assumes that the initial wet-bulb temperature is uniform. If the value is a two-element vector, then the block assumes that the initial wet-bulb temperature varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial humidity specification to Wet-bulb temperature.

Initial trace gas specification — Method to describe initial trace gas level

Mass fraction (default) | Mole fraction

Method used to describe the trace gas level at the start of simulation.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and clear the Initialize to nominal operating conditions check box.

Initial trace gas mass fraction — Mass fraction of trace gas at start of simulation

0.001 (default) | scalar in the range [0,1] | two-element vector

Mass fraction of trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mass fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mass fraction varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial trace gas specification to Mass fraction.

Initial trace gas mole fraction — Mole fraction of trace gas at start of simulation

0.001 (default) | scalar in the range [0,1] | two-element vector

Mole fraction of the trace gas in a moist air mixture at the start of simulation. If the value is a scalar, then the block assumes that the initial mole fraction is uniform. If the value is a two-element vector, then the block assumes that the initial mole fraction varies linearly between the ports, with the first element corresponding to port Ae and the second element corresponding to port Be.

The block ignores this parameter if the Trace gas model parameter in the Moist Air Properties (MA) block is None.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air, clear the Initialize to nominal operating conditions check box, and set Initial trace gas specification to Mole fraction.

Initial mass ratio of water droplets to moist air — Ratio of water droplets to moist air

0 (default) | positive scalar

Initial mass ratio of water droplets to moist air.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air and clear the Initialize to nominal operating conditions check box.

Initial evaporator wall temperature — Evaporator surface temperature at simulation start

293.15 K (default) | positive scalar | two-element vector

Heat transfer surface temperature at the start of simulation. If it this value is a scalar, the block assumes that the initial temperature is uniform. If this value is a two-element vector, then the block assumes that the temperature varies linearly between ports Ae and Be with the first element corresponding to Ae and second element corresponding to Be.

Dependencies

To enable this parameter, clear the Initialize to nominal operating conditions and Evaporator wall thermal mass check boxes.

Relative humidity at saturation — Relative humidity point of condensation

1 (default) | nonnegative scalar

Relative humidity point of condensation. Condensation occurs above this value. In most cases, this value is 1, which is equivalent to 100%. A value greater than 1 indicates a supersaturated vapor.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air.

Water vapor condensation time constant — Time scale for condensation

1e-3 s (default) | positive scalar

Characteristic time scale at which an oversaturated moist air volume returns to saturation by condensing out excess humidity.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air.

Water droplets evaporation time constant — Time scale for evaporation

1e-3 s (default) | positive scalar

Characteristic time scale at which water droplets evaporate to vapor.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air.

Fraction of condensate entrained as water droplets — Fraction of condensate in water droplets

1 (default) | scalar in the range [0,1]

Fraction of the condensate in the moist air that is entrained as water droplets.

Dependencies

To enable this parameter, set External fluid for evaporator heat transfer to Moist air.

Correlation Coefficients

Modify condenser Nusselt number correlation coefficients — Whether to modify condenser Nusselt number correlation coefficients

Off (default) | On

Whether to manually modify the condenser Nusselt number correlation coefficients. Select this parameter to adjust the off-design performance of the condenser.

a in Nu = a*Re^b*Pr^c for refrigerant, liquid regime — Correlation coefficient for refrigerant subcooled liquid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for a subcooled liquid for the condenser. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

a in Nu = a*Re^b*Pr^c for refrigerant, mixture regime — Correlation coefficient for refrigerant liquid-vapor mixture

0.005 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the liquid-vapor mixture for the condenser. The default value is based on the Cavallini and Zecchin correlation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

a in Nu = a*Re^b*Pr^c for refrigerant, vapor regime — Correlation coefficient for refrigerant superheated vapor

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the superheated vapor for the condenser. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

b in Nu = a*Re^b*Pr^c for refrigerant — Reynolds number exponent in correlation for refrigerant

0.8 (default) | positive scalar

Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

c in Nu = a*Re^b*Pr^c for refrigerant — Prandtl number exponent in correlation for refrigerant

0.33 (default) | positive scalar

Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for condenser refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

a in Nu = a*Re^b*Pr^c for external fluid, liquid regime — Correlation coefficient for subcooled liquid in two-phase fluid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the subcooled condenser external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients and set External fluid for condenser heat transfer to Two-phase fluid.

a in Nu = a*Re^b*Pr^c for external fluid, mixture regime — Correlation coefficient for liquid-vapor mixture in two-phase fluid

0.005 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for liquid-vapor mixture in the condenser external fluid. The default value is based on the Cavallini and Zecchin correlation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients and set External fluid for condenser heat transfer to Two-phase fluid.

a in Nu = a*Re^b*Pr^c for external fluid, vapor regime — Correlation coefficient for superheated vapor in two-phase fluid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for superheated vapor in the condenser external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients and set External fluid for condenser heat transfer to Two-phase fluid.

a in Nu = a*Re^b*Pr^c for external fluid — Correlation coefficient for condenser external fluid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients and set External fluid for condenser heat transfer to Moist air or Thermal liquid.

b in Nu = a*Re^b*Pr^c for external fluid — Reynolds number exponent in correlation for condenser external fluid

0.8 (default) | positive scalar

Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

c in Nu = a*Re^b*Pr^c for external fluid — Prandtl number exponent in correlation for condenser external fluid

0.33 (default) | positive scalar

Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the condenser external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify condenser Nusselt number correlation coefficients.

Modify evaporator Nusselt number correlation coefficients — Whether to modify evaporator Nusselt number correlation coefficients

Off (default) | On

Whether to manually modify the evaporator Nusselt number correlation coefficients. Select this parameter to adjust the off-design performance of the evaporator.

a in Nu = a*Re^b*Pr^c for refrigerant, liquid regime — Correlation coefficient for refrigerant subcooled liquid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for a subcooled liquid for the evaporator. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.

a in Nu = a*Re^b*Pr^c for refrigerant, mixture regime — Correlation coefficient for refrigerant liquid-vapor mixture

0.005 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the liquid-vapor mixture for the evaporator. The default value is based on the Cavallini and Zecchin correlation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.

a in Nu = a*Re^b*Pr^c for refrigerant, vapor regime — Correlation coefficient for refrigerant superheated vapor

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the superheated vapor for the condenser. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.

b in Nu = a*Re^b*Pr^c for refrigerant — Reynolds number exponent in correlation for refrigerant

0.8 (default) | positive scalar

Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.

c in Nu = a*Re^b*Pr^c for refrigerant — Prandtl number exponent in correlation for refrigerant

0.33 (default) | positive scalar

Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for evaporator refrigerant. The same value applies to subcooled liquid, liquid-vapor mixture, and superheated vapor.

Dependencies

To enable this parameter, select External fluid for evaporator heat transfer.

a in Nu = a*Re^b*Pr^c for external fluid, liquid regime — Correlation coefficient for subcooled liquid in two-phase fluid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the subcooled evaporator external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients and set External fluid for evaporator heat transfer to Two-phase fluid.

a in Nu = a*Re^b*Pr^c for external fluid, mixture regime — Correlation coefficient for liquid-vapor mixture in two-phase fluid

0.005 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for liquid-vapor mixture in the evaporator external fluid. The default value is based on the Cavallini and Zecchin correlation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients and set External fluid for evaporator heat transfer to Two-phase fluid.

a in Nu = a*Re^b*Pr^c for external fluid, vapor regime — Correlation coefficient for superheated vapor in two-phase fluid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for superheated vapor in the evaporator external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients and set External fluid for evaporator heat transfer to Two-phase fluid.

a in Nu = a*Re^b*Pr^c for external fluid — Correlation coefficient for evaporator external fluid

0.023 (default) | positive scalar

Proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients and set External fluid for evaporator heat transfer to Moist air or Thermal liquid.

b in Nu = a*Re^b*Pr^c for external fluid — Reynolds number exponent in correlation for evaporator external fluid

0.8 (default) | positive scalar

Reynolds number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.

c in Nu = a*Re^b*Pr^c for external fluid — Prandtl number exponent in correlation for evaporator external fluid

0.33 (default) | positive scalar

Prandtl number exponent in the correlation of the Nusselt number as a function of the Reynolds number and Prandtl number for the evaporator external fluid. The default value is based on the Colburn equation.

Dependencies

To enable this parameter, select Modify evaporator Nusselt number correlation coefficients.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2023a

R2024b: Model water droplets suspended in moist air flow

Blocks in the moist air domain can now model water droplets suspended in a moist air flow. To enable droplet tracking, select Enable entrained water droplets in the Moist Air Properties (MA) block connected to your moist air network.

R2024a: New moisture specification option

The block has new options for the Inlet humidity specification and Initial humidity specification parameters for both the condenser and evaporator external fluids. This option, called Wet-bulb temperature, allows you to input data in the form of a wet-bulb temperature.